The invention generally relates to the eradication of contaminants using photodynamic therapy. The invention also generally relates to the processing of whole blood and its components for storage and transfusion. In a more specific sense, the invention relates to the extracorporeal treatment of collected whole blood and its components with photoactive materials to eradicate viruses and other pathogenic contaminants.
With the coming of blood component therapy, most whole blood collected today is separated into its clinically proven components for storage and administration. The clinically proven components of whole blood include red blood cells, used to treat chronic anemia; platelet-poor plasma, from which Clotting Factor VIII-rich cryoprecipitate can be obtained for the treatment of hemophilia; and concentrations of platelets, used to control thrombocytopenic bleeding.
It is well known that blood can carry infectious agents like hepatitis-B virus; the human immunodeficiency (AIDS) virus; the Herpes virus; and the influenza virus. To avoid the transmission of these infectious agents during blood transfusions, donors of blood are routinely screened and also undergo serologic testing to detect the presence of these agents. Still, it is difficult to always assure that these infectious agents are detected.
The use of photodynamic therapy has been suggested as a way to eradicate infectious agents from collected blood and its components. See Matthews et al, xe2x80x9cPhotodynamic Therapy of Viral Contaminants With Potential for Blood Bank Applications,xe2x80x9d Transfusion, 28(1), pp. 81-83 (1988). Various extracorporeal systems have been proposed that use photodynamic therapy to treat blood prior to storage and transfusion. See, for example, Edelson U.S. Pat. Nos. 4,613,322 and 4,684,521; Troutner et al U.S. Pat. No. 4,708,715; Wiesehahn et al U.S. Pat. No. 4,727,027; Sieber U.S. Pat. Nos. 4,775,625 and 4,915,683; and Judy et al U.S. Pat. No. 4,878,891.
To date, there has been a general lack of success in economically adapting the benefits of photodynamic therapy to the demands of the blood banking industry. One reason for this is that not all biological contaminants are carried free within the blood where they can be readily coupled to photoactive agents. Some biological contaminants are entrained on or within white blood cells out of the reach of photoactive agents.
The extracorporeal systems proposed to date can eradicate only contaminants that are carried free within the blood. Prior systems have not provided a device that can remove both free and entrained biological contaminants from a fluid in a single pass through a single treatment zone.
For this and other reasons, the promise of photodynamic therapy in treating the nation""s banked blood supply has gone largely unfulfilled.
The invention provides improved systems and methods for treating plasma to remove contaminants such as leukocytes and adventitious viral agents, which can be carried free within the plasma or entrained within the leukocytes in the plasma.
One aspect of the invention treats fresh frozen plasma by thawing the plasma and filtering the thawed plasma to remove leukocytes and thereby remove viral agents entrained in the leukocytes.
In a preferred embodiment, the systems and methods add a photoactive material to the thawed plasma. The emission of radiation at a selected wavelength into the thawed plasma activates the photoactive material to eliminate viral agents that are carried free in the plasma.
Another aspect of the invention provides systems and methods for treating plasma carrying contaminants and leukocytes that are capable of entraining contaminants. The systems and methods separate leukocytes from the plasma by filtration, thereby removing contaminants entrained within leukocytes. The systems and methods also add to the plasma a photoactive material and emit radiation at a selected wavelength into the plasma to activate the photoactive material and thereby eradicate the contaminant that is free of entrainment by leukocytes.
In a preferred embodiment, the filter includes a prefilter layer that also removes aggregates larger than leukocytes from thawed plasma. The filter also includes, in a downstream flow direction from the prefilter, a material having pores sized to remove leukocytes from thawed plasma by exclusion.
In a preferred embodiment, the material comprises polyether sulfone forming two layers, with the pores of the first upstream layer being larger than the pores of the second downstream layer. In a preferred embodiment, the pores of the first layer are about 1.2 xcexcm in size and the pores of the second layer are about 0.8 xcexcm in size.
Other features and advantages of the invention will be pointed out in, or will be apparent from, the drawings, specification and claims that follow.